The present invention relates to a bogie frame for a railway vehicle, and in particular a bogie frame for a railway vehicle and provided with side and horizontal beams constituting the bogie frame formed of fiber reinforced plastics to reduce the entire weight of the bogie frame of the railway vehicle.
Usually, the bogie frame of a railway vehicle or a rolling stock is mainly of steel plates, but recently, bogie frames are manufactured by utilizing fiber reinforced plastic material (called hereinlater "FRP") to reduce the total weight thereof such as disclosed in Japanese Patent Laid-Open Publication No. 90771/1981 or No. 143257/1986.
The former publication (90771/1981) discloses a bogie frame for a railway vehicle, in which the bogie frame is integrally constructed by an H-shaped member made from FRP and an axle of the bogie is elastically supported by utilizing the elasticity of the H-shaped member itself without using a specific axle supporting member such as a leaf spring for the purpose of reducing the whole weight of the bogie frame.
The later publication (143257/1986) also discloses a bogie frame for a railway vehicle, in which the bogie frame is made from FRP so that a flexural rigidity thereof corresponds to that of a spring constant of an axle spring formed of ordinary materials.
In a case where the bogie frame for the railway vehicle is manufactured by utilizing FRP, it is required to harmonize the two contradicting factors of maintaining the strength of the bogie frame and reducing the weight thereof in addition to cost problem. Namely, with respect to the strength of the bogie frame, it is necessary to have sufficient strength against the concentration of stress applied to joined portions between horizontal beams and side beams constituting the bogie frame. A solution to this problem has been proposed in Japanese Patent Laid-Open Publication No. 139567/1985 or No. 46971/1988, for example.
However, the integral manufacture of the bogie frame by utilizing the FRP and the location of an additional rib to obtain sufficient strength against the concentration of the stress applied to the joined portion between the side and horizontal beams results in an increase of the manufacturing cost for the bogie frame of the railway vehicle. In another aspect, it was difficult to obtain sufficient strength by forming the horizontal and side beams individually with FRP and by joining them together afterwards.